Most web resources are intended for use by desktop and laptop personal computers (PCs). This means they are often unsuitable for use by mobile communication devices. Web resources, typically web sites and web pages, may include elements such as script, graphics, animations, video data, audio data, layouts etc. that are not supported by a mobile communication device. For example, a web site may include an object encoded using Java® or Adobe® Flash script, but a mobile communication device may not have the correct software to use such an object. Similarly, an image on a web site may be too large to be displayed on a mobile communication device.
In light of this, web resources specifically encoded for use by mobile communication devices are sometimes provided. Usually, web resources specifically encoded for use by mobile communication devices are based on web resources intended for use by PCs. For example, an organisation may have two web sites, one for use by PCs and the other specifically encoded for use by mobile communication devices. There is therefore duplication of effort in providing the same content for use by both PCs and mobile communication devices. For this reason, only large and well resourced organisations or those with a particular reason to target mobile communication devices tend to provide web resources that are specifically encoded for mobile communication devices. There is therefore a need to make it easier to provide web resources suitable for use by mobile communication devices.
In order to address this need, it is known to convert web resources intended for use by PCs to be suitable for use by mobile communication devices. This conversion is known as transcoding. In one example, the transcoding is carried out by a mobile network operator, although transcoding can be carried out by other entities, such as search engines or third parties that offer a transcoding service. When the user of a mobile communication device seeks to retrieve a given web resource via the mobile communication network, instead of the mobile communication device being provided with the web resource itself, it is provided with a transcoded version of the web resource.
In more detail, the mobile communication device may send a request for a web resource, which request includes an internet domain name, e.g. “www.bobspizzashop.com”. The mobile network retrieves the web resource from the web server using the internet domain name (or, more specifically, an Internet Protocol (IP) address for the server at which the web resource is located, which IP address can be retrieved from the domain name system (DNS) of the internet using the internet domain name). However, instead of delivering the web resource straight to the mobile communication device, the mobile communication network first transcodes the web resource.
Typically, the transcoding involves identifying the type of mobile communication device that made the request and adapting the web resource to be suitable for that device. For example, if the web resource is encoded using script that is not supported by the type of mobile communication device, the web resource may be converted to script that is supported by the mobile communication device. Similarly, an image included in the web resource may be resized to suit the limitations of the display of the mobile communication device.
Although transcoding can significantly improve the presentation of web resources to users of mobile communication devices, the results are not always ideal. The variety and complexity of web resources designed for PCs is such that there is great difficulty in providing a transcoding system that is able to produce effective results in all circumstances.
Moreover, transcoding is often undertaken independently of the owner of the web resource. As such, the owner of the web resource has little control over the results of the transcoding process. Accordingly, the owners of web resources cannot control user experience of their web resources.
It is known to use style sheets to allow a single web resource to be rendered differently by different browsers. A style sheet is a programming construct used to control the presentation of elements provided in mark-up language, such as hypertext mark-up language (HTML). When a browser renders a web resource, such as a web page, it uses rules contained in the style sheet to determine how to present elements provided in mark-up language. In order to effect this styling, a style sheet class is included in the web page to identify a given element, while the style sheet itself provides the rules as to how elements having this style sheet class should be rendered. For example, the initial text in the web page might be identified by the style sheet class “heading” and the style sheet for the style sheet class “heading” might indicate the font size or colour of the text.
A conventional style sheet language is known as cascading style sheets (CSS). CSS specifies a priority scheme to determine which rule is applied to a style sheet class when more than one rule is provided for that style sheet class. In practice, the different rules may originate from different style sheets. This priority scheme gives rise to the cascade from which CSS gets its name. Different browsers may therefore apply different rules from the style sheet, leading to different presentation of the web resource.
However, style sheets only provide limited assistance in the provision of web resources to a mobile communication device. In particular, style sheets do not modify a web resource optimised for use by PCs before it is delivered to the mobile communication device. Instead, style sheets only take effect when the web resource is rendered by the mobile communication device. This limits the value of the style sheets, as the mobile communication device must download the web resource before applying any rules contained in the style sheets. For example, where a web resource optimised for a PC contains an object encoded using Java® or Adobe® Flash script that cannot be displayed by the mobile communication device, the use of style sheets will not prevent that object being downloaded to the mobile communication device, even if it will prevent any effort being made to display it. This is an unnecessary drain on the bandwidth of the mobile communication device's connection to the internet. Effective use of such bandwidth is of particular importance in the context of mobile communication devices.